This invention relates in general to transportation systems and in particular to an intermodal railway system utilizing closed containers to carry bulk materials, particularly municipal solid waste, by truck and rail.
The disposal of municipal solid waste (MSW) such as common garbage and trash as well as sludge produced by water treatment facilities is becoming an increasingly important and difficult problem as landfilled sites convenient to urban centers are becoming full and environmental protection concerns are foreclosing the ocean dumping of solid refuse. At present, the most common MSW disposal system is to simply haul the MSW by tractor (transfer) trailer from an urban collection point or treatment plant to a landfill. Given the capital cost of a "transfer trailer" and typical current operating costs per mile for a typical 22 ton load, currently there is approximately a 300 mile one way haul distance limit on economically feasible disposal sites.
Because the tonnage that can be hauled by truck in a single load is limited by highway and bridge laws, the cost of transporting bulk waste by truck is inherently limited as to its volume and weight. While railroads can carry larger loads, measured both in volume and in weight, over long distances, to date efforts to use railway cars for hauling low value bulk materials, particularly loose MSW, has proven to be financially uneconomical. At present there is substantially no use of railroads to haul municipal solid waste. Indeed, at present the maximum payload that is carried by any standard railway car is about 60 tons, regardless of the type of car or the nature of its load.
One known approach to utilizing railroads for bulk transportation is a convertible trailer which has detachable rail wheels and specialized interconnections so that the highway trailer can be converted into a railroad car. An example of this type of unit is a product sold by the Thrall Car Company under the trade designation "Roadrailer". While the system has found some market for hauling high value items, it is not economical for transportation of bulk materials. The detachable wheels and special interconnection systems to convert the "transfer trailer" into a "railroad car" significantly increases the capital cost of each unit required to transport a given weight, e.g., the 22 tons normally carried by a "transfer trailer" when hauling MSW. Also, the converted "cars" do not operate in conjunction with existing railroad service; they must operate as a complete train and there is currently in the U.S. a required minimum shipment level of 60 units. Further, charges for railway transport of a single "car" of this type carrying 22 tons is equivalent to that of a single railway car operating in a "piggy back" mode carrying approximately twice the payload.
Well known transportation systems utilizing railways also include the use of dedicated railway car such as box cars, gondolas, and hoppers. Such cars have a long-standing history in transporting loose bulk materials such as coal, ores, ash, sludge, salt, and grain products. One major problem, however, is the loading and unloading of the bulk material from the car. If the cars are not open topped, loading through side doors is inherently difficult for a loose bulk material. If the car has an open top, loading may be simple, but unloading can still be a problem.
Certain loads can be removed with a clamshell scoop, but this process is slow and has significant capital costs. Another solution is movable openings or doors such as a "walking floor" or the conventional "push out" system. These techniques, while being perhaps the fastest, nevertheless, if installed require about 10 minutes to complete the unloading of one car. To date, no one has built and used commercially such a "push out"/"walking floor" rail car. Moreover, whenever there are moving parts there is liquid leakage, buckling of the door or other closure, latching requirements, and the possibility of malfunction. Another approach is simply to lift and dump an entire railroad car. While this system is obviously fast and effective, it also requires a substantial capital investment. With an installation presently costing close to $1 million for MSW disposal, each landfill would need a railroad line and one of these installations. Further, box cars or open-top cars which have doors or other removable openings which are hinged and/or latched experience problems in that they leak, the doors buckle, and the doors can open unintentionally losing material or presenting a hazard to personnel working with the cars.
Open-top cars also have other problems. The material can be blown out of the car. Rain and contaminants can enter the car directly spoiling the contents if they are not waste products or, if they are waste products, adding to the liquid contained in the car which may present a leaking or odor problem. Sabotage, theft and spontaneous combustion (a special concern when transporting bulk combustibles such as coal which produces coal dust) are other problems that appear depending on the nature of the material transported. One common solution is simply to cover the open car with a tarpaulin, but tarpaulins are frequently lost or break free in transit. These conditions allow a loss of the material being carried and all of the other problems noted above. Further, tarpaulins require personnel time to install and remove them.
Still another approach, intended principally to control the loss of material due to the wind during transport, has been to bail the MSW or other loose bulk material prior to loading it into the cars. However, it typically requires 8 to 12 hours to load the bails into a car and another 8 to 12 hours to remove them, plus the cost of bailing.
A general problem with all specialized railroad cars is that they are not intermodal, that is, the railroad car cannot move on the highway. Therefore unless the railroad car can be brought directly to a loading facility, the entire system requires that conventional trucks be loaded and haul the material to a loading site at a railroad terminal. This therefore involves the cost of truck hauling as well as the personnel and capital cost for equipment to load and unload the MSW or other bulk material to and from the trailer, and then the railroad car.
Flatbed railway cars carrying trailers ("TOFC"--Trailer-on-Flatcar), or what is commonly termed "piggy back" systems, attempt to provide an intermodal transportation system using rail. In this system, typically two trailers are loaded onto a single flatbed car to provide a total carrying weight of approximately 44 tons. While this avoids loading and unloading of the material from the trailer, this arrangement is nevertheless comparatively costly and time consuming. It is necessary to have special TOFC cars, special terminals equipped to load and unload the trailers from the cars, and once the trailers are loaded, they are typically intransit for 10 days, as compared to a typical intransit time to 2 days if the trailer is operated on the highways. Since the capital cost of two trailers is substantial (currently about $90,000), this extra 8 days period of inactivity itself represents a considerable cost increase. More generally, TOFC is a system limited by the load carrying capacity of highway vehicles, which in turn are limited by highway and bridge limitations. It does not take full advantage of the weight and volume capacity of traditional railroad equipment. Therefore TOFC systems have proven useful principally for transporting high value food and manufactured materials, but have not been used for transporting low value bulk materials such as MSW.
Container-on-flatcar ("COFC") systems are also currently in use to provide intermodal transportation. Special containers carry goods on trucks and are then moved onto COFC cars. However, COFC containers heretofore have required special four-corner, personnel-activated restraints which space the containers approximately 9 inches above the deck of the flat car. This has a disadvantage in that it produces extreme pressure points on the deck coincident with the points of support of the containers. Also the force of the wind, particularly when the train is moving, acts under the containers and produces a force that tends to lift the containers from the car. Known COFC systems could reach a maximum pay load of 60 tons for railcar, as compared to typically pay load of 44 tons for TOFC carrying two trailers, but COFC systems do not provide the volume, weight and loading/unloading advantages to make them economically advantageous for bulk material transport. Also, currently available systems are not readily adapted to the rapid, convenient and low cost loading and unloading of bulk materials. They are not open-topped and they have doors or other movable closures with latches.
It is therefore a principal object of the present invention to provide a transportation system for loose bulk materials, particularly low value, loose, municipal solid waste, which is cost effective for these materials in terms of capital and operating costs.
Another principal object of the invention is to provide an intermodal loading system which provides an extremely rapid and complete unloading of the bulk material without fixed capital intensive equipment such installations to dump entire railway cars.
A further object of the invention is to provide the foregoing advantages while avoiding a loss of bulk material intransit and reliable resistance to penetration of moisture or other liquids to the material.
A further object of the invention is to provide a transportation system with the foregoing advantages which also prevents the leakage of liquids from the system.
Yet another object of the invention is to provide a system with the foregoing advantages which utilizes no doors, hinges, walking floors, or more generally, any openings in the side or bottom of the vehicle or container holding the bulk material.
Yet another object of the invention is to provide a transportation system that makes the hauling of loose bulk materials, particularly low value materials such as MSW, by railway economically competitive with existing systems.
Yet another object of the present invention is to provide a system with the foregoing advantages which can carry volume and tonnages per railway car higher than heretofore known.
Still another object of the invention is to provide a bulk materials transport system which is rugged, reliable, and extremely simple to use.
A further object of the invention is to provide a bulk transport system which is highly resistant to spontaneous combustion, sabotage, or theft.
A still further object of the invention is to provide intermodal bulk material transport system which is highly crash resistant and provides a low clean-up exposure.
Another object of the invention is to provide an intermodal transport system for bulk materials which is sufficiently cost effective, including capital and operating cost as measured by cost per ton per mile transported, that remote and heretofore unusable waste disposal sites become available.